Topic
Organic matter
About: Organic matter is a research topic. Over the lifetime, 45516 publications have been published within this topic receiving 1640069 citations. The topic is also known as: organic material & natural organic matter, NOM.
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TL;DR: The POM fraction was isolated by dispersing the soil in 5 g L-1 hexametaphosphate and passing the dispersed soil samples through a 53-micrometer sieve as mentioned in this paper.
Abstract: Many models have been constructed in an attempt to describe the dynamics of soil organic-matter (SOM) turnover, most of which include 2 to 3 kinetically defined organic-matter pools. Physical and chemical definition of these conceptualized SOM pools has been difficult. We describe a simple method for dispersion of soil to isolate a particulate organic-matter (POM) fraction that may represent an important SOM pool in grassland soils. The POM fraction was isolated by dispersing the soil in 5 g L-1 hexametaphosphate and passing the dispersed soil samples through a 53-micrometer sieve. We compared POM and mineral-associated C among three tillage treatments (20 yr under cultivation) and an undisturbed grassland at Sidney, NE. The POM C in the native sod represented 39% of the total soil organic C. Twenty years of bare-fallow, stubble-mulch, and no-till management reduced the C content in this fraction to 18, 19, and 25%, respectively, of the total organic C. The mineral-associated organic-matter fraction showed no reduction in C content in the bare-fallow treatment compared with the grassland soil but increased in the no-till and stubble-mulch treatments. Nitrogen dynamics generally mirrored those observed for C. Analysis of the POM fraction for lignin and cellulose content indicated that this fraction was 47% lignin and had a lignocellulose index of 0.7. The stable C-isotope composition of the POM fraction suggests that wheat-derived POM turns over faster than grass-derived POM. We suggest the POM fraction closely matches the characteristics of a SOM pool variously described as slow, decomposable, or stabilized organic matter
2,259 citations
TL;DR: The cell content of 12 bacterial phospholipid fatty acids (PLFA) was determined in bacteria extracted from soil by homogenization/centrifugation and the soil content of the PLFA 18:2ω6 was correlated with the ergosterol content, which supports the use of this PLFA as an indicator of fungal biomass.
Abstract: The cell content of 12 bacterial phospholipid fatty acids (PLFA) was determined in bacteria extracted from soil by homogenization/centrifugation. The bacteria were enumerated using acridine orange direct counts. An average of 1.40×10-17 mol bacterial PLFA cell-1 was found in bacteria extracted from 15 soils covering a wide range of pH and organic matter contents. With this factor, the bacterial biomass based on PLFA analyses of whole soil samples was calculated as 1.0–4.8 mg bacterial C g-1 soil C. The corresponding range based on microscopical counts was 0.3–3.0 mg bacterial C g-1 soil C. The recovery of bacteria from the soils using homogenization/centrifugation was 2.6–16% (mean 8.7%) measured by PLFA analysis, and 12–61% (mean 26%) measured as microscopical counts. The soil content of the PLFA 18:2ω6 was correlated with the ergosterol content (r=0.92), which supports the use of this PLFA as an indicator of fungal biomass. The ratio 18:2ω6 to bacterial PLFA is therefore suggested as an index of the fungal:bacterial biomass ratio in soil. An advantage with the method based on PLFA analyses is that the same technique and even the same sample is used to determine both fungi and bacteria. The fungal:bacterial biomass ratio calculated in this way was positively correlated with the organic matter content of the soils (r=0.94).
2,256 citations
TL;DR: In this article, it was shown that organic matter appears to be the major control on pyrite formation in normal (non-euxinic) terrigenous marine sediments where dissolved sulfate and iron minerals are abundant.
2,234 citations
TL;DR: For example, in a recent paper as discussed by the authors, the authors investigated the mechanisms governing sedimentary organic matter preservation in marine sediments and found that organic preservation in the marine environment is < 0.5% efficient, and that the factors which directly determine preservation vary with depositional regime, but have in common a critical interaction between organic and inorganic materials over locally variable time scales.
2,216 citations
TL;DR: In this article, the authors summarize the recent literature about controls on dissolved organic matter (DOM) concentrations and fluxes in so-called "soil degraded organic matter" (SOCOM).
Abstract: Dissolved organic matter (DOM) in soils plays an important role in the biogeochemistry of carbon, nitrogen, and phosphorus, in pedogenesis, and in the transport of pollutants in soils. The aim of this review is to summarize the recent literature about controls on DOM concentrations and fluxes in soi
2,138 citations